Many conventional navigation systems estimate travel time for routes to assist the user in time management. For example, a simplistic travel time estimate can be derived by dividing the length of the route by the posted speed limit of the route. Such a time estimate often includes error due to a variety of variables that are not accounted for in the computation, such as road conditions, traffic congestion, driving patterns, accuracy of navigation system, etc.
Some navigation systems use traffic time providers to provide more accurate travel times. These providers often use cell phone probes and wireless cell phone networks to estimate travel times for highways and roadways. One system, for example, traces specific, anonymous vehicles, and uses a sequence of cellular messages to correlate the cell phones to the route traveled. Once a cell phone is correlated to a route, the system can measure the position of the cell phone and travel time samples can be generated for various segments of the route. If the travel time samples are averaged over long periods of time then the travel time samples can lead to large errors in travel times estimates. Moreover, publicly available studies have shown that travel time estimation using cell phones as data probes may not be accurate in heavy traffic conditions due to the inability to accurately track position.
Some navigation systems allow users to enter parameters related to the user's specific driving habits. These parameters, however, do not take into account local traffic patterns and changes in the user's driving habits based on time of day, season or other factors that could alter the user's driving habits.